Oncogenic role of the frizzled-7/beta-catenin pathway in hepatocellular carcinoma

SIRT7 stabilizes β-catenin and promotes canonical Wnt activation via upregulating FZD7

AIMS

The dysregulated Wnt/β-Catenin signaling pathway leads to occurrence of various diseases, and abnormal activation of β-Catenin is a major characteristic of human HCC. FZD7 is a positive regulator of the Wnt/β-catenin signaling pathway, and its upregulation is related to increase of β-catenin expression and carcinogenesis in human HCC. However, mechanisms underlying FZD7 upregulation in HCC remain elusive.

MAIN METHODS

Nuclear cytosol fractionation, immunofluorescence and Top-Flash were used to detect the activation of β-Catenin. Protein half-life and ubiquitination assays were applied to evaluate protein stability. RNA-seq combined with qRT-PCR was used to evaluate differential gene expressions after SIRT7 knockdown. Wound healing and transwell assays were used to measure cancer cell migration.

KEY FINDINGS

SIRT7-mediated FZD7 expression is essential for stability and activation of β-catenin. Knockdown SIRT7 in HCC cells resulted in enhanced binding of β-catenin to the DC, decreased its stability, nuclear localization and activation. Knockdown FZD7 reversed SIRT7 overexpression mediated β-catenin stabilization and impairment of binding of β-catenin to the DC. At molecular level, SIRT7 promotes FZD7 expression via upregulating transcription factor PU.1, knockdown PU.1 abolished SIRT7-mediated upregulation of FZD7. Finally, we confirmed that FZD7 was responsible for SIRT7-mediated β-catenin stabilization and HCC cells migration. By using clinical samples, we observed strong positive correlations between SIRT7 and PU.1, FZD7, p-GSK3β and β-Catenin in human HCC.

SIGNIFICANCE

Our results thus revealed a previously undisclosed role of SIRT7 in regulating the canonical Wnt/β-catenin signaling pathway, thereby offering additional evidence that SIRT7 holds promise as a novel therapeutic target for human HCC.

Wnt Signaling in Hepatocellular Carcinoma: Biological Mechanisms and Therapeutic Opportunities

Hepatocellular carcinoma (HCC), characterized by significant morbidity and mortality rates, poses a substantial threat to human health. The expression of ligands and receptors within the classical and non-classical Wnt signaling pathways plays an important role in HCC. The Wnt signaling pathway is essential for regulating multiple biological processes in HCC, including proliferation, invasion, migration, tumor microenvironment modulation, epithelial-mesenchymal transition (EMT), stem cell characteristics, and autophagy. Molecular agents that specifically target the Wnt signaling pathway have demonstrated significant potential for the treatment of HCC. However, the precise mechanism by which the Wnt signaling pathway interacts with HCC remains unclear. In this paper, we review the alteration of the Wnt signaling pathway in HCC, the mechanism of Wnt pathway action in HCC, and molecular agents targeting the Wnt pathway. This paper provides a theoretical foundation for identifying molecular agents targeting the Wnt pathway in hepatocellular carcinoma.

Frizzled-3 suppression overcomes multidrug chemoresistance by Wnt/β-catenin signaling pathway inhibition in hepatocellular carcinoma cells

Multidrug resistance (MDR) is a major obstacle to the efficacy of hepatocellular carcinoma (HCC) chemotherapy. Previous studies have identified that low FZD3 predicted decreased survival after intraperitoneal versus intravenous-only chemotherapy in ovarian cancer. This study aimed to identify a potential target in HCC chemotherapy. The FZD3 expression variant in HCC cell lines was detected by RT-qPCR and western blotting. The FZD3 expression in the early recurrent HCC group (RE group) and the non-early recurrent HCC group (non-RE group) was measured by RT-qPCR. Then, the 50% inhibitory concentrations (IC50) in HCC cell lines were studied by MTT assay. TOP/FOP FLASH luciferase assay was performed to measure TCF-binding activities. We found that FZD3 was upregulated in three HCC cell lines, and the FZD3 expression was significantly higher in the RE group than in the non-RE group (P = 0.0344). A positive correlation between FZD3 and MDR1 was observed in HCC tissues (R2 = 0.6368, P = 0.0001). Then, we found that FZD3 knockdown significantly altered Huh-7 cell chemotherapeutic sensitivity to cisplatin [50.43 µM in the FZD3 siRNA (siFZD3) group vs 98.59 µM in the siRNA negative control (siNC) group; P = 0.007] or doxorubicin (7.43 µM in the siFZD3 group vs 14.93 µM in the siNC group; P = 0.017). TOP/FOP FLASH luciferase assay showed FZD3 could inhibit Wnt/β-catenin signaling in HCC cells. Moreover, FZD3 expression knockdown in SNU-449 and Huh-7 cells markedly reduced β-catenin and phosho-β-catenin (S37) protein expression, and Cyclin D1, c-myc and MDR1 were significantly decreased. This is the first study to describe the significantly increased FZD3 expression in patients with early recurrent HCC. FZD3 knockdown led to increased sensitivity to chemotherapy by Wnt/β-catenin signaling inhibition in HCC cell lines. Our study suggests FZD3 as a potential target for reversing chemoresistance in HCC.

GPC3 gene expression and allelic discrimination of FZD7 gene in Egyptian patients with hepatocellular carcinoma

Background

Hepatocellular carcinoma (HCC) is the second leading cause of cancer-related deaths worldwide, and especially in Egypt. Early diagnosis of HCC greatly improves the survival and prognosis of patients. Low sensitivity and specificity of alpha-fetoprotein (AFP) has led to the demand for novel biomarkers of HCC. The aim of the present study was to evaluate the validity of frizzled-7 (FZD7) and glypican-3 (GPC3) gene expression as potential biomarkers for HCC early diagnosis, and to investigate the association between FZD7 rs2280509 polymorphism and HCC risk.

Materials and methods

Quantification of FZD7 and GPC3 gene expression by real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) assay, and genotyping FZD 7 (rs2280509 SNP) gene polymorphism using RT-PCR.

Results

The current results revealed that FZD7 gene expression had a greater area under the curve (AUC) for identifying HCC than GPC3 gene expression and AFP levels. The combination of the three markers as a panel showed a better diagnostic performance with a greater AUC than any of the single markers alone (p < 0.05). The FZD7 rs2280509 polymorphism (CT) was found to be significantly associated with an increased risk of HCC. The CT genotype and T allele were significantly more prevalent in the HCC group compared to either the cirrhosis (p = 0.03) or control groups (p = 0.0009 and 0.002; respectively).

Conclusion

FZD7 and GPC3 gene expressions have a complementary role in early HCC detection, with a greater diagnostic sensitivity and accuracy than AFP. In addition, FZD7 rs2280509 polymorphism is significantly associated with an increased risk of HCC in the Egyptian population.

PRECLINICAL MODELS OF LIVER CÂNCER

•In this review, we described different murine models of carcinogenesis: classic models, new transgenic and combined models, that reproduce the key points for HCC and CCA genesis allowing a better understanding of its genetic physiopathological, and environmental abnormalities. •Each model has its advantages, disadvantages, similarities, and differences with the corresponding human disease and should be chosen according to the specificity of the study. Ultimately, those models can also be used for testing new anticancer therapeutic approaches. •Cholangiocarcinoma has been highlighted, with an increase in prevalence. This review has an important role in understanding the pathophysiology and the development of new drugs. Background - This manuscript provides an overview of liver carcinogenesis in murine models of hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA). Objective - A review through MEDLINE and EMBASE was performed to assess articles until August 2022.Methods - Search was conducted of the entire electronic databases and the keywords used was HCC, CCA, carcinogenesis, animal models and liver. Articles exclusion was based on the lack of close relation to the subject. Carcinogenesis models of HCC include HCC induced by senescence in transgenic animals, HCC diet-induced, HCC induced by chemotoxicagents, xenograft, oncogenes, and HCC in transgenic animals inoculated with B and C virus. The models of CCA include the use of dimethylnitrosamine (DMN), diethylnitrosamine (DEN), thioacetamide (TAA), and carbon tetrachloride (CCl4). CCA murine models may also be induced by: CCA cells, genetic manipulation, Smad4, PTEN and p53 knockout, xenograft, and DEN-left median bile duct ligation. Results - In this review, we described different murine models of carcinogenesis that reproduce the key points for HCC and CCA genesis allowing a better understanding of its genetic, physiopathological, and environmental abnormalities. Conclusion - Each model has its advantages, disadvantages, similarities, and differences with the corresponding human disease and should be chosen according to the specificity of the study. Ultimately, those models can also be used for testing new anticancer therapeutic approaches.

Circular RNA ACTN4 promotes intrahepatic cholangiocarcinoma progression by recruiting YBX1 to initiate FZD7 transcription

BACKGROUND & AIMS

Intrahepatic cholangiocarcinoma (ICC) is a primary liver cancer with high aggressiveness and extremely poor prognosis. The role of circular RNAs (circRNAs) in ICC carcinogenesis and progression remains to be determined.

METHODS

CircRNA microarray was performed to screen significantly upregulated circRNAs in paired ICC and non-tumor tissues. Colony formation, transwell, and xenograft models were used to examine the role of circRNAs in ICC proliferation and metastasis. RNA pulldown, mass spectrometry, chromatin immunoprecipitation, RNA-binding protein immunoprecipitation, chromatin isolation by RNA purification, electrophoretic mobility shift assay, and luciferase reporter assays were used to explore the molecular sponge role of the circRNA (via miRNA binding), and the interaction between circRNA and RNA-binding proteins.

RESULTS

Hsa_circ_0050898, which originated from exon 1 to exon 20 of the ACTN4 gene (named circACTN4), was significantly upregulated in ICC. High circACTN4 expression was associated with enhanced tumor proliferation and metastasis in vitro and in vivo, as well as a worse prognosis following ICC resection. In addition, circACTN4 upregulated Yes-associated protein 1 (YAP1) expression by sponging miR-424-5p. More importantly, circACTN4 also recruited Y-box binding protein 1 (YBX1) to stimulate Frizzled-7 (FZD7) transcription. Furthermore, circACTN4 overexpression in ICC cells enhanced the interaction between YAP1 and β-catenin, which are the core components of the Hippo and Wnt signaling pathways, respectively.

CONCLUSIONS

CircACTN4 was upregulated in ICC and promoted ICC proliferation and metastasis by acting as a molecular sponge of miR-424-5p, as well as by interacting with YBX1 to transcriptionally activate FZD7. These results suggest that circACTN4 is a potential prognostic marker and therapeutic target for ICC.

LAY SUMMARY

Intrahepatic cholangiocarcinoma is a primary liver cancer associated with aggressiveness and extremely poor prognosis. It is essential for therapeutic development that we uncover relevant pathogenic pathways. Herein, we showed that a circular RNA (circACTN4) was highly expressed in intrahepatic cholangiocarcinoma and was positively associated with tumor growth and metastasis through key developmental signaling pathways. Thus, circACTN4 could be a prognostic biomarker and therapeutic target for intrahepatic cholangiocarcinoma.

A FZD7-specific Antibody-Drug Conjugate Induces Ovarian Tumor Regression in Preclinical Models

Although WNT signaling is frequently dysregulated in solid tumors, drugging this pathway has been challenging due to off-tumor effects. Current clinical pan-WNT inhibitors are nonspecific and lead to adverse effects, highlighting the urgent need for more specific WNT pathway-targeting strategies. We identified elevated expression of the WNT receptor Frizzled class receptor 7 (FZD7) in multiple solid cancers in The Cancer Genome Atlas, particularly in the mesenchymal and proliferative subtypes of ovarian serous cystadenocarcinoma, which correlate with poorer median patient survival. Moreover, we observed increased FZD7 protein expression in ovarian tumors compared with normal ovarian tissue, indicating that FZD7 may be a tumor-specific antigen. We therefore developed a novel antibody-drug conjugate, septuximab vedotin (F7-ADC), which is composed of a chimeric human-mouse antibody to human FZD7 conjugated to the microtubule-inhibiting drug monomethyl auristatin E (MMAE). F7-ADC selectively binds human FZD7, potently kills ovarian cancer cells in vitro, and induces regression of ovarian tumor xenografts in murine models. To evaluate F7-ADC toxicity in vivo, we generated mice harboring a modified Fzd7 gene where the resulting Fzd7 protein is reactive with the human-targeting F7-ADC. F7-ADC treatment of these mice did not induce acute toxicities, indicating a potentially favorable safety profile in patients. Overall, our data suggest that the antibody-drug conjugate approach may be a powerful strategy to combat FZD7-expressing ovarian cancers in the clinic.

Targeting TRIM54/Axin1/β-Catenin Axis Prohibits Proliferation and Metastasis in Hepatocellular Carcinoma

Accumulating evidence demonstrates that dysregulation of ubiquitin-mediated degradation of oncogene or suppressors plays an important role in several diseases. However, the function and molecular mechanisms of ubiquitin ligases underlying hepatocellular carcinoma (HCC) remain elusive. In the current study, we show that overexpression of TRIM54 was associated with HCC progression. TRIM54 overexpression facilitates proliferation and lung metastasis; however, inhibition of TRIM54 significantly suppressed HCC progression both in vitro and in vivo. Mechanically, we demonstrated that TRIM54 directly interacts with Axis inhibition proteins 1 (Axin1) and induces E3 ligase-dependent proteasomal turnover of Axin1 and substantially induces sustained activation of wnt/β-catenin in HCC cell lines. Furthermore, we showed that inhibition of the wnt/β-catenin signaling pathway via small molecule inhibitors significantly suppressed TRIM54-induced proliferation. Our data suggest that TRIM54 might function as an oncogenic gene and targeting the TRIM54/Axin1/β-catenin axis signaling may be a promising prognostic factor and a valuable therapeutic target for HCC.

Unlocking the Wnt pathway: Therapeutic potential of selective targeting FZD7 in cancer

The Wnt signaling is of paramount pathophysiological importance. Despite showing promising anticancer activities in pre-clinical studies, current Wnt pathway inhibitors face complications in clinical trials resulting from on-target toxicity. Hence, the targeting of pathway component(s) that are essential for cancer but dispensable for normal physiology is key to the development of a safe Wnt signaling inhibitor. Frizzled₇ (FZD₇) is a Wnt pathway receptor that is redundant in healthy tissues but crucial in various cancers. FZD₇ modulates diverse aspects of carcinogenesis, including cancer growth, metastasis, maintenance of cancer stem cells, and chemoresistance. In this review, we describe state-of-the-art knowledge of the functions of FZD₇ in carcinogenesis and adult tissue homeostasis. Next, we overview the development of small molecules and biomolecules that target FZD₇. Finally, we discuss challenges and possibilities in developing FZD₇-selective antagonists.

ANGPTL8 roles in proliferation, metabolic diseases, hypothyroidism, polycystic ovary syndrome, and signaling pathways

A new and atypical member of the ANGPTL family is angiopoietin-like protein 8 (ANGPTL8). This newly discovered hormone is a drug target that can be used to treat diabetes and dyslipidemia. The protein, as a hepatocyte-derived circulating factor, can control the triglyceride level of plasma. ANGPTL8 is significantly associated with inflammation and metabolic syndrome consequences such as obesity, diabetes, hypothyroidism, and PCOS. ANGPTL8 gene has four exons encoding a 22/5 kDa weight of 198 amino acid polypeptides. A highly preserved ANGPTL8 gene among mammals exhibits the essential hormone functions of ANGPTL8. Nevertheless, the physiological function of this hormone in the body is poorly understood. Studies published in PubMed (2008-2020), Google Scholar (2004-2020), and Scopus (2004-2020) databases of clinical trials were reviewed. This analysis is aimed at collecting information on ANGPTL8. The emphasis of this review was on gathering information about the role of ANGPTL8 in the metabolism of glucose and lipids and cell proliferation. It addition to the different roles of ANGPTL8 in diabetes and lipid metabolism, this review emphasized on the protein role in signaling pathways. The study also proposes the signaling pathways that may be considered as a new target for treatment.

Frizzled-7 Identifies Platinum-Tolerant Ovarian Cancer Cells Susceptible to Ferroptosis

Defining traits of platinum-tolerant cancer cells could expose new treatment vulnerabilities. Here, new markers associated with platinum-tolerant cells and tumors were identified using in vitro and in vivo ovarian cancer models treated repetitively with carboplatin and validated in human specimens. Platinum-tolerant cells and tumors were enriched in ALDH+ cells, formed more spheroids, and expressed increased levels of stemness-related transcription factors compared with parental cells. Additionally, platinum-tolerant cells and tumors exhibited expression of the Wnt receptor Frizzled-7 (FZD7). Knockdown of FZD7 improved sensitivity to platinum, decreased spheroid formation, and delayed tumor initiation. The molecular signature distinguishing FZD7+ from FZD7- cells included epithelial-to-mesenchymal (EMT), stemness, and oxidative phosphorylation-enriched gene sets. Overexpression of FZD7 activated the oncogenic factor Tp63, driving upregulation of glutathione metabolism pathways, including glutathione peroxidase 4 (GPX4), which protected cells from chemotherapy-induced oxidative stress. FZD7+ platinum-tolerant ovarian cancer cells were more sensitive and underwent ferroptosis after treatment with GPX4 inhibitors. FZD7, Tp63, and glutathione metabolism gene sets were strongly correlated in the ovarian cancer Tumor Cancer Genome Atlas (TCGA) database and in residual human ovarian cancer specimens after chemotherapy. These results support the existence of a platinum-tolerant cell population with partial cancer stem cell features, characterized by FZD7 expression and dependent on the FZD7-β-catenin-Tp63-GPX4 pathway for survival. The findings reveal a novel therapeutic vulnerability of platinum-tolerant cancer cells and provide new insight into a potential "persister cancer cell" phenotype. SIGNIFICANCE: Frizzled-7 marks platinum-tolerant cancer cells harboring stemness features and altered glutathione metabolism that depend on GPX4 for survival and are highly susceptible to ferroptosis.

WNT Signalling in Osteoarthritis and Its Pharmacological Targeting

Osteoarthritis (OA) is a highly disabling musculoskeletal condition affecting millions of people worldwide. OA is characterised by progressive destruction and irreversible morphological changes of joint tissues and architecture. At molecular level, de-regulation of several pathways contributes to the disruption of tissue homeostasis in the joint. Overactivation of the WNT/β-catenin signalling pathway has been associated with degenerative processes in OA. However, the multiple layers of complexity in the modulation of the signalling and the still insufficient knowledge of the specific molecular drivers of pathogenetic mechanisms have made difficult the pharmacological targeting of this pathway for therapeutic purposes. This review aims to provide an overview of the WNT/β-catenin signalling in OA with a particular focus on its role in the articular cartilage. Pathway components whose targeting showed therapeutic potential will be highlighted and described. A specific section will be dedicated to Lorecivivint, the first inhibitor of the β-catenin-dependent pathway currently in phase III clinical trial as OA-modifying agent.

lncRNA VIM‑AS1 promotes cell proliferation, metastasis and epithelial‑mesenchymal transition by activating the Wnt/β‑catenin pathway in gastric cancer

The present study aimed to explore the biological functions and molecular mechanisms of the long non-coding RNA VIM antisense RNA 1 (VIM-AS1) in gastric cancer (GC). The expression of VIM-AS1 was analyzed in tissues from patients with GC and GC cell lines by reverse transcription-quantitative (RT-q)PCR. The relationship between VIM-AS1 expression and overall survival time of patients with GC was also assessed. To determine the biological functions of VIM-AS1, Cell Counting Kit-8 assay, colony formation assay, flow cytometry, wound healing assay and Transwell assay were employed. The targeting relationship among VIM-AS1, microRNA (miR)-8052 and frizzled 1 (FZD1) was verified by the dual luciferase reporter gene assay. The underlying molecular mechanism of VIM-AS1 on GC was determined by RT-qPCR and western blotting. In addition, tumor formation was detected in nude mice. The results of the present study demonstrated that VIM-AS1 was highly expressed in GC tissues and cells. In addition, VIM-AS1 expression was demonstrated to be closely related to the prognosis of patients with GC. Notably, silencing VIM-AS1 inhibited the proliferation, migration and invasion, and enhanced apoptosis of AGS and HGC-27 cells. Silencing VIM-AS1 significantly increased the protein expression levels of cleaved caspase-3, Bax and E-cadherin, but decreased the protein expression levels of Bcl-2, N-cadherin, vimentin, matrix metalloproteinase (MMP)-2, MMP-9, β-catenin, cyclin D1, C-myc and FZD1. Additionally, silencing VIM-AS1 inhibited tumor growth in nude mice. Cumulatively, the present study demonstrated that VIM-AS1 may promote cell proliferation, migration, invasion and epithelial-mesenchymal transition by regulating FDZ1 and activating the Wnt/β-catenin pathway in GC.

LncRNA LEF1-AS1 promotes metastasis of prostatic carcinoma via the Wnt/β-catenin pathway

BACKGROUND

Long noncoding RNAs (lncRNAs) are important functional regulators of many biological processes of cancers. However, the mechanisms by which lncRNAs modulate androgen-independent prostate cancer (AIPC) development remain largely unknown.

METHODS

Next-generation sequencing technology and RT-qPCR were used to assess LEF1-AS1 expression level in AIPC tissues and adjacent normal tissues. Functional in vitro experiments, including colony formation, EDU and transwell assays were performed to assess the role of LEF1-AS1 in AIPC. Xenograft assays were conducted to assess the effect of LEF1-AS1 on cell proliferation in vivo. Chromatin immunoprecipitation (ChIP) and RNA binding protein immunoprecipitation (RIP) assays were performed to elucidate the regulatory network of LEF1-AS1.

RESULTS

The next-generation sequencing results showed that LEF1-AS1 is significantly overexpressed in AIPC. Furthermore, our RT-qPCR assay data showed that LEF1-AS1 is overexpressed in AIPC tissues. Functional experiments showed that LEF1-AS1 promotes the proliferation, migration, invasion and angiogenic ability of AIPC cells in vitro and tumour growth in vivo by recruiting the transcription factor C-myb to the promoter of FZD2, inducing its transcription. Furthermore, LEF1-AS1 was shown to function as a competing endogenous RNA (ceRNA) that sponges miR-328 to activate CD44.

CONCLUSION

In summary, the results of our present study revealed that LEF1-AS1 acts as a tumour promoter in the progression of AIPC. Furthermore, the results revealed that LEF1-AS1 functions as a ceRNA and regulates Wnt/β-catenin pathway activity via FZD2 and CD44. Our results provide new insights into the mechanism that links the function of LEF1-AS1 with AIPC and suggests that LEF1-AS1 may serve as a novel potential target for the improvement of AIPC therapy.

Frizzled Receptors in Tumors, Focusing on Signaling, Roles, Modulation Mechanisms, and Targeted Therapies

Wnt molecules play crucial roles in development and adult homeostasis through their receptors Frizzled proteins (Fzds). Fzds mediate canonical β-catenin pathway and various noncanonical β-catenin-independent pathways. Aberrant Fzd signaling is involved in many diseases including cancer. Wnt/β-catenin is a well-established oncogenic pathway involved in almost every aspect of tumor development. However, Fzd-mediated noncanonical Wnt pathways function as both tumor promoters and tumor suppressors depending on cellular context. Fzd-targeted therapies have proven to be effective on cultured tumor cells, tumor cell xenografts, mouse tumor models, and patient-derived xenografts (PDX). Moreover, Fzd-targeted therapies synergize with chemotherapy in preclinical models. However, the occurrence of fragility fractures in patients treated with Fzd-targeted agents such as OMP-54F28 and OMP-18R5 limits the development of this combination. Along with new insights on signaling, roles, and modulation mechanisms of Fzds in human tumors, more Fzd-related therapeutic targets will be developed.

Non-canonical Fzd7 signaling contributes to breast cancer mesenchymal-like stemness involving Col6a1

Mesenchymal-like stemness is characterized by epithelial-mesenchymal transition (EMT). Breast cancer (BC) cell mesenchymal-like stemness is responsible for distal lung metastasis. Interrogation of databases showed that Fzd7 was closely associated with a panel of mesenchymal-related genes and a panel of stemness-related genes. Fzd7 knockdown in mesenchymal-like MDA-MB-231 and Hs578T cells reduced expression of Vimentin, Slug and Zeb1, induced an epithelial-like morphology, inhibited cell motility, impaired mammosphere formation and decreased Lgr5⁺ subpopulation. In contrast, Fzd7 overexpression in MCF7 cells resulted in opposite changes. Fzd7 knockdown delayed xenograft tumor formation, suppressed tumor growth, and impaired lung metastasis. Mechanistically, Fzd7 combined with Wnt5a/b and modulated expression of phosphorylated Stat3 (p-STAT3), Smad3 and Yes-associated protein 1 (Yap1). Moreover, Fzd7-Wnt5b modulated expression of collagen, type VI, alpha 1 (Col6a1). Both Wnt5b knockdown and Col6a1 knockdown disrupted BC cell mesenchymal phenotype and stemness. Taken together, Fzd7 contributes to BC cell EMT and stemness, inducing tumorigenesis and metastasis, mainly through a non-canonical Wnt5b pathway. Col6a1 is implicated in Fzd7-Wnt5b signaling, and mediates Fzd7-Wnt5b -induced mesenchymal-like stemness.

The Hepatitis B Virus Pre-Core Protein p22 Activates Wnt Signaling

An emerging theme for Wnt-addicted cancers is that the pathway is regulated at multiple steps via various mechanisms. Infection with hepatitis B virus (HBV) is a major risk factor for liver cancer, as is deregulated Wnt signaling, however, the interaction between these two causes is poorly understood. To investigate this interaction, we screened the effect of the various HBV proteins for their effect on Wnt/β-catenin signaling and identified the pre-core protein p22 as a novel and potent activator of TCF/β-catenin transcription. The effect of p22 on TCF/β-catenin transcription was dose dependent and inhibited by dominant-negative TCF4. HBV p22 activated synthetic and native Wnt target gene promoter reporters, and TCF/β-catenin target gene expression in vivo. Importantly, HBV p22 activated Wnt signaling on its own and in addition to Wnt or β-catenin induced Wnt signaling. Furthermore, HBV p22 elevated TCF/β-catenin transcription above constitutive activation in colon cancer cells due to mutations in downstream genes of the Wnt pathway, namely APC and CTNNB1. Collectively, our data identifies a previously unappreciated role for the HBV pre-core protein p22 in elevating Wnt signaling. Understanding the molecular mechanisms of p22 activity will provide insight into how Wnt signaling is fine-tuned in cancer.

Antiepileptic Drug Carbamazepine Binds to a Novel Pocket on the Wnt Receptor Frizzled-8

Misregulation of Wnt signaling is common in human cancer. The development of small molecule inhibitors against the Wnt receptor, frizzled (FZD), may have potential in cancer therapy. During small molecule screens, we observed binding of carbamazepine to the cysteine-rich domain (CRD) of the Wnt receptor FZD8 using surface plasmon resonance (SPR). Cellular functional assays demonstrated that carbamazepine can suppress FZD8-mediated Wnt/β-catenin signaling. We determined the crystal structure of the complex at 1.7 Å resolution, which reveals that carbamazepine binds at a novel pocket on the FZD8 CRD. The unique residue Tyr52 discriminates FZD8 from the closely related FZD5 and other FZDs for carbamazepine binding. The first small molecule-bound FZD structure provides a basis for anti-FZD drug development. Furthermore, the observed carbamazepine-mediated Wnt signaling inhibition may help to explain the phenomenon of bone loss and increased adipogenesis in some patients during long-term carbamazepine treatment.

Clinical implications of cancer stem cells in digestive cancers: acquisition of stemness and prognostic impact

Digestive system cancers are the most frequent cancers worldwide and often associated with poor prognosis because of their invasive and metastatic characteristics. Recent studies have found that the plasticity of cancer cells can impart cancer stem-like properties via the epithelial-mesenchymal transition (EMT). Cancer stem-like properties such as tumor initiation are integral to the formation of metastasis, which is the main cause of poor prognosis. Numerous markers of cancer stem cells (CSCs) have been identified in many types of cancer. Therefore, CSCs, via their stem cell-like functions, may play an important role in prognosis after surgery. While several reports have described prognostic analysis using CSC markers, few reviews have summarized CSCs and their association with prognosis. Herein, we review the prognostic potential of eight CSC markers, CD133, CD44, CD90, ALDH1A1, EPCAM, SOX2, SOX9, and LGR5, in digestive cancers including those of the pancreas, colon, liver, gastric, and esophagus.

Cell Surface Proteins in Hepatocellular Carcinoma: From Bench to Bedside

Cell surface proteins act as the go-between in carrying the information from the extracellular environment to the intracellular signaling proteins. However, these proteins are often deregulated in neoplastic diseases, including hepatocellular carcinoma. This review discusses several recent studies that have investigated the role of cell surface proteins in the occurrence and progression of HCC, highlighting the possibility to use them as biomarkers of the disease and/or targets for vaccines and therapeutics.

Toll-like receptor 3 downregulation is an escape mechanism from apoptosis during hepatocarcinogenesis

BACKGROUND & AIMS

Low levels of toll-like receptor 3 (TLR3) in patients with hepatocellular carcinoma (HCC) are associated with poor prognosis, primarily owing to the loss of inflammatory signaling and subsequent lack of immune cell recruitment to the liver. Herein, we explore the role of TLR3-triggered apoptosis in HCC cells.

METHODS

Quantitative reverse transcription PCR, western blotting, immunohistochemistry and comparative genomic hybridization were used to analyze human and mouse HCC cell lines, as well as surgically resected primary human HCCs, and to study the impact of TLR3 expression on patient outcomes. Functional analyses were performed in HCC cells, following the restoration of TLR3 by lentiviral transduction. The role of TLR3-triggered apoptosis in HCC was analyzed in vivo in a transgenic mouse model of HCC.

RESULTS

Lower expression of TLR3 in tumor compared to non-tumor matched tissue was observed at both mRNA and protein levels in primary HCC, and was predictive of shorter recurrence-free survival after surgical resection in both univariate (hazard ratio [HR] 1.79; 95% CI 1.04-3.06; p = 0.03) and multivariate analyses (HR 1.73; CI 1.01-2.97; p = 0.04). Immunohistochemistry confirmed frequent downregulation of TLR3 in human and mouse primary HCC cells. None of the 6 human HCC cell lines analyzed expressed TLR3, and ectopic expression of TLR3 following lentiviral transduction not only restored the inflammatory response but also sensitized cells to TLR3-triggered apoptosis. Lastly, in the transgenic mouse model of HCC, absence of TLR3 expression was accompanied by a lower rate of preneoplastic hepatocyte apoptosis and accelerated hepatocarcinogenesis without altering the tumor immune infiltrate.

CONCLUSION

Downregulation of TLR3 protects transforming hepatocytes from direct TLR3-triggered apoptosis, thereby contributing to hepatocarcinogenesis and poor patient outcome.

LAY SUMMARY

Hepatocellular carcinoma (HCC) is a heterogeneous disease associated with a poor prognosis. In patients with HCC, TLR3 downregulation is associated with reduced survival. Herein, we show that the absence of TLR3 is associated with a lower rate of apoptosis, and subsequently more rapid hepatocarcinogenesis, without any change to the immune infiltrate in the liver. Therefore, the poor prognosis associated with low TLR3 expression in HCC is likely linked to tumors ability to escape apoptosis. TLR3 may become a promising therapeutic target in TLR3-positive HCC.

Isolation and characterization of a new basal-like luminal progenitor in human breast tissue

Background

Adult stem cells and progenitors are responsible for breast tissue regeneration. Human breast epithelial progenitors are organized in a lineage hierarchy consisting of bipotent progenitors (BPs), myoepithelial- and luminal-restricted progenitors (LRPs) where the LRP differentiation into mature luminal cells requires estrogen receptor (ER) signaling. However, the experimental evidence exploring the relationship between the BPs and LRPs has remained elusive. In this study, we report the presence of a basal-like luminal progenitor (BLP) in human breast epithelial cells.

Methods

Breast reduction samples were used to obtain different subsets of human breast epithelial cell based on cell surface marker expression using flow cytometry. Loss of function and gain of function studies were employed to demonstrate the role of NOTCH3 (NR3)-FRIZZLED7 (FZD7) signaling in luminal cell fate commitment.

Results

Our results suggest that, NR3-FZD7 signaling axis was necessary for luminal cell fate commitment. Similar to LRPs, BLPs (NR3^highFZD7^highCD90⁺MUC1⁻ER⁻) differentiate to generate NR3^medFZD7^medCD90⁻MUC1⁺ER⁺ luminal cells. Unlike LRPs however, BLP’s proliferation and differentiation potentials depend on NR3 and regulated in part by FZD7 signaling. Lastly, we show that BLPs have a higher colony-forming potential than LRPs and that they are continuously generated from the NOTCH3⁻FZD7^low subset of the bipotent progenitors.

Conclusion

Our data indicate that BPs differentiate to generate basal-like luminal progenitors that in turn differentiate into LRPs. These results provide new insights into the hierarchical organization of human breast epithelial cell and how cooperation between the Notch and Wnt signaling pathways define a new progenitor cell type.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1361-3) contains supplementary material, which is available to authorized users.

miR-504 suppresses mesenchymal phenotype of glioblastoma by directly targeting the FZD7-mediated Wnt-β-catenin pathway

Background

MicroRNAs (miRNAs) play crucial roles in tumor initiation and development. Previously, we indicated that miR-504 is downregulated and suppresses tumor proliferation in glioblastoma (GBM). However, the regulation and relevant mechanism of miR-504 in GBM mesenchymal (ME) transition remain unclear.

Methods

Transcriptome and clinical data were obtained from The Cancer Genome Atlas (TCGA) database. The potential functions of miR-504 were predicted using gene ontology analysis. GBM cell migration and invasion were examined using wound healing and Transwell assays. Epithelial–mesenchymal transition (EMT) progression in GBM cell lines was detected with immunofluorescence and western blotting. The stemness activity of glioma stem-like cells (GSCs) was assessed by sphere formation assay and tumor xenograft model. miR-504 binding to the FZD7 (frizzled class receptor 7) 3′ untranslated region (3′UTR) was validated using dual luciferase reporter assay. TOP/FOP Flash assays were conducted to determine the effects of miR-504 on Wnt/β-catenin signaling.

Results

Analysis of TCGA transcriptomic data showed that low miR-504 expression correlated with ME subtype transition and poor survival in patients with GBM. Functional experiments showed that miR-504 overexpression suppressed malignant behaviors of GBM cells, such as migration, invasion, EMT, and stemness activity. Furthermore, miR-504 was a negative regulator of the Wnt–β-catenin pathway by directly repressing FZD7 expression, and FZD7 overexpression reversed the EMT inhibition caused by miR-504. Moreover, the low miR-504/FZD7 expression ratio was a ME subtype marker and could serve as a significant prognostic indicator and predict the clinical outcome of chemotherapy and radiotherapy for patients with GBM in TCGA dataset.

Conclusions

Our results suggest that miR-504 suppresses the aggressive biological processes associated with the ME phenotype of GBM and could be a potential candidate for therapeutic applications in these malignant brain tumors.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1370-1) contains supplementary material, which is available to authorized users.

miR-186 modulates hepatocellular carcinoma cell proliferation and mobility via targeting MCRS1-mediated Wnt/β-catenin signaling

Previous studies have revealed that miR-186 is involved in the pathogenesis of many malignancies. However, the role of miR-186 in hepatocellular carcinoma (HCC) carcinogenesis and its detailed mechanism are poorly understood. This study was to investigate the function of miR-186 in modulating HCC cell proliferation, cell cycle, migration, and invasion. We found that miR-186 was decreased in HCC tissues and cell lines. Loss-of-function experiments showed that reduction of miR-186 dramatically enhanced tumor cell proliferation and metastasis. Besides, miR-186 also participated in the modulation of the cell cycle. In addition, luciferase reporter assays and Western blot analysis showed that MCRS1 was a novel target of miR-186 in HCC cells. Notably, upregulation of miR-186 suppressed the nuclear β-catenin accumulation and blocked the activation of Wnt/β-catenin signaling in HCC cells. Forced MCRS1 expression abrogated the inhibitory effect of miR-186 on cell growth, metastasis and Wnt/β-catenin signaling in HCC cells. Our findings may provide new insight into the pathogenesis of HCC and miR-186/ MCRS1 might function as new therapeutic targets for HCC.

The FZD7-TWIST1 axis is responsible for anoikis resistance and tumorigenesis in ovarian carcinoma

Frizzled family receptor 7 (FZD7), a Wnt signaling receptor, is associated with the maintenance of stem cell properties and cancer progression. FZD7 has emerged as a potential therapeutic target because it is capable of transducing both canonical and noncanonical Wnt signals. In this study, we investigated the regulatory pathway downstream of FZD7 and its functional roles. We found that FZD7 expression was crucial to the maintenance of the mesenchymal phenotype, anoikis resistance, and spheroid and tumor formation in ovarian cancer (OC). We identified TWIST1 as the crucial downstream effector of the FZD7 pathway. TWIST1, a basic helix loop helix transcription factor, is known to associate with mesenchymal and cancer stem cell phenotypes. Manipulating TWIST1 expression mimicked the functional consequences observed in the FZD7 model, and overexpression of TWIST1 partially rescued the functional phenotypes abolished by FZD7 knockdown. We further proved that FZD7 regulated TWIST1 expression through epigenetic modifications of H3K4me3 and H3K27ac at the TWIST1 proximal promoter. We also identified that the FZD7‐TWIST1 axis regulates the expression of BCL2, a gene that controls apoptosis. Identification of this FZD7‐TWIST1‐BCL2 pathway reaffirms the mechanism of anoikis resistance in OC. We subsequently showed that the FZD7‐TWIST1 axis can be targeted by using a small molecule inhibitor of porcupine, an enzyme essential for secretion and functional activation of Wnts. In conclusion, our results identified that the FZD7‐TWIST1 axis is important for tumorigenesis and anoikis resistance, and therapeutic inhibition results in cell death in OCs.

Overexpression of FZD1 and CAIX are Associated with Invasion, Metastasis, and Poor-Prognosis of the Pancreatic Ductal Adenocarcinoma

Approximately 80% of patients with pancreatic ductal adenocarcinoma (PDAC) have metastatic disease with poor prognosis, but clinically available biomarkers have not yet been identified. This study was to investigate the clinical significance of FZD1 and CAIX in PDACs. FZD1 and CAIX protein expression was measured using EnVision immunohistochemistry. Positive FZD1 or CAIX expression was significantly higher in PDAC than that in precursor lesions (p < 0.01). Positive FZD1 or CAIX expression was significantly lower in cases with well-differentiated adenocarcinoma, no-metastasis of the lymph node, no-invasion of regional tissues, and TNM I/II stage disease than in cases with poorly-differentiated adenocarcinoma, metastasis and invasion, and TNM stage III+ IV stage disease (p < 0.05 or p < 0.01). The expression of FZD1 positively correlated with CAIX in PDAC (P = 0.000). Univariate Kaplan-Meier analysis showed that FZD1 and/or CAIX expression (p < 0.001) was significantly associated with shorter overall survival (p < 0.05). Cox multivariate analysis showed that differentiation, tumor mass, lymph node metastasis, invasion, TNM stage, FZD1 and CAIX levels negatively correlated with overall survival. Positive FZD1 and CAIX expressions are poor prognostic factors in PDAC patients. FZD1 and CAIX might be important biological markers for the carcinogenesis, metastasis, invasion, and prognosis of PDAC.

MicroRNA-504 functions as a tumor suppressor in hepatocellular carcinoma through inhibiting Frizzled-7-mediated-Wnt/β-catenin signaling

Accumulating evidence suggests that microRNAs (miRNAs) are critical regulators in the development and progression of various malignant tumors, including hepatocellular carcinoma (HCC). Multiple findings have indicated that miRNA-504 (miR-504) is dysregulated in several types of cancers, functioning as an oncogenic miRNA or a tumor suppressive miRNA. However, the role of miR-504 in HCC remains unknown. In this study, we aimed to detect the expression pattern of miR-504 in HCC tissues and cell lines and investigate the precise biological function in HCC cells. Our results showed that miR-504 expression levels were frequently downregulated in both HCC tissues and cell lines. Gain-of-function experiments demonstrated that miR-504 overexpression inhibited the proliferation and invasion in HCC cell lines. By contrast, miR-504 inhibition had the opposite effect. Interestingly, bioinformatics analysis predicted that Frizzled-7 (FZD7) was a potential target gene of miR-504. Dual-luciferase reporter assays confirmed that miR-504 directly targeted the 3'-untranslated region of FZD7 mRNA. In addition, our results showed that miR-504 negatively regulated the mRNA and protein expression of FZD7 in HCC cell lines. Moreover, miR-540 overexpression inhibited the cellular expression of β-catenin and blocked the activation of Wnt signaling in HCC cells. Notably, restoration of FZD7 expression significantly reversed the inhibitory effect of miR-504 on proliferation, invasion, and Wnt/β-catenin signaling in HCC cells. In conclusion, our results demonstrate that miR-504 functions as a tumor suppressive miRNA that inhibits the proliferation and invasion of HCC cells by targeting FZD7 and inhibiting Wnt/β-catenin signaling. Our study provides evidence that miR-504-meidated FZD7/Wnt/β-catenin signaling pathway plays an important role in HCC development and progression and suggests miR-504 as a novel future therapeutic target for treatment of HCC.

Tissue Tranglutaminase Regulates Interactions between Ovarian Cancer Stem Cells and the Tumor Niche

Cancer progression and recurrence are linked to a rare population of cancer stem cells (CSC). Here, we hypothesized that interactions with the extracellular matrix drive CSC proliferation and tumor-initiating capacity and investigated the functions of scaffold protein tissue transglutaminase (TG2) in ovarian CSC. Complexes formed by TG2, fibronectin (FN), and integrin β1 were enriched in ovarian CSC and detectable in tumors. A function-inhibiting antibody against the TG2 FN-binding domain suppressed complex formation, CSC proliferation as spheroids, tumor-initiating capacity, and stemness-associated Wnt/β-catenin signaling. Disruption of the interaction between TG2 and FN also blocked spheroid formation and the response to Wnt ligands. TG2 and the Wnt receptor Frizzled 7 (Fzd7) form a complex in cancer cells and tumors, leading to Wnt pathway activation. Protein docking and peptide inhibition demonstrate that the interaction between TG2 and Fzd7 overlaps with the FN-binding domain of TG2. These results support a new function of TG2 in ovarian CSC, linked to spheroid proliferation and tumor-initiating capacity and mediated through direct interactions with Fzd7. We propose this complex as a new stem cell target.Significance: These findings reveal a new mechanism by which ovarian CSCs interact with the tumor microenvironment, promoting cell proliferation and tumor initiation. Cancer Res; 78(11); 2990-3001. ©2018 AACR.

Cripto-1 contributes to stemness in hepatocellular carcinoma by stabilizing Dishevelled-3 and activating Wnt/β-catenin pathway

Identification and characterization of functional molecular targets conferring stemness properties in hepatocellular carcinoma (HCC) offers crucial insights to overcome the major hurdles of tumor recurrence, metastasis and chemoresistance in clinical management. In the current study, we investigated the significance of Cripto-1 in contributing to HCC stemness. Cripto-1 was upregulated in the sorafenib-resistant clones derived from HCC cell lines and patient-derived xenograft that we previously developed, suggesting an association between Cripto-1 and stemness. By in vitro experiments, Cripto-1 fostered cell proliferation, migration, and invasion. It also enhanced self-renewal ability and conferred chemoresistance of HCC cells. Consistently, silencing of Cripto-1 suppressed in vivo tumorigenicity on serial transplantation. On the downstream signaling mechanism, expression of major components of Wnt/β-catenin pathway β-catenin, AXIN2, and C-MYC, accompanied by β-catenin activity was reduced upon Cripto-1 knockdown. The suppressive effects on stemness properties with Cripto-1 knockdown in vitro and in vivo were partially rescued by forced expression of constitutively active β-catenin. Further elucidation revealed the binding of Cripto-1 to Frizzled-7 (FZD7), low-density lipoprotein receptor-related protein 6 (LRP6) and Dishevelled-3 (DVL3) of the Wnt/β-catenin pathway and stabilized DVL3 protein. Analyses with clinical samples validated Cripto-1 overexpression in HCC tissues, as well as a positive correlation between Cripto-1 and AXIN2 expressions. High Cripto-1 level in tumor was associated with poorer disease-free survival of HCC patients. Taken together, Cripto-1 binds to FZD7/LRP6 and DVL3, stabilizes DVL3 expression and activates the Wnt/β-catenin signaling cascade to confer stemness in HCC. Our study findings substantiated the role of Cripto-1 in determining stemness phenotypes of HCC and mechanistically in modulating the Wnt/β-catenin signaling cascade, one of the most frequently deregulated pathways in liver cancer.

Deregulation of Frizzled Receptors in Hepatocellular Carcinoma

G protein-coupled receptors (GPCRs) have a substantial role in tumorigenesis and are described as a “cancer driver”. Aberrant expression or activation of GPCRs leads to the deregulation of downstream signaling pathways, thereby promoting cancer progression. In hepatocellular carcinoma (HCC), the Wnt signaling pathway is frequently activated and it is associated with an aggressive HCC phenotype. Frizzled (FZD) receptors, a family member of GPCRs, are known to mediate Wnt signaling. Accumulating findings have revealed the deregulation of FZD receptors in HCC and their functional roles have been implicated in HCC progression. Given the important role of FZD receptors in HCC, we summarize here the expression pattern of FZD receptors in HCC and their corresponding functional roles during HCC progression. We also further review and highlight the potential targeting of FZD receptors as an alternative therapeutic strategy in HCC.

Frizzled2 signaling regulates growth of high-risk neuroblastomas by interfering with β-catenin-dependent and β-catenin-independent signaling pathways

Frizzled2 (FZD2) is a receptor for Wnts and may activate both canonical and non-canonical Wnt signaling pathways in cancer. However, no studies have reported an association between FZD2 signaling and high-risk NB so far. Here we report that FZD2 signaling pathways are critical to NB growth in MYCN-single copy SK-N-AS and MYCN-amplified SK-N-DZ high-risk NB cells. We demonstrate that stimulation of FZD2 by Wnt3a and Wnt5a regulates β-catenin-dependent and -independent Wnt signaling factors. FZD2 blockade suppressed β-catenin-dependent signaling activity and increased phosphorylation of PKC, AKT and ERK in vitro, consistent with upregulation of β-catenin-independent signaling activity. Finally, FZD2 small interfering RNA knockdown suppressed tumor growth in murine NB xenograft models associated with suppressed β-catenin-dependent signaling and a less vascularized phenotype in both NB xenografts. Together, our study suggests a role for FZD2 in high-risk NB cell growth and provides a potential candidate for therapeutic inhibition in FZD2-expressing NB patients.

Sox9 confers stemness properties in hepatocellular carcinoma through Frizzled-7 mediated Wnt/β-catenin signaling

Sox9, an SRY-related HMG box transcription factor, is a progenitor/precursor cell marker of the liver expressed during embryogenesis and following liver injury. In this study, we investigated the role of Sox9 and its molecular mechanism with reference to stemness properties in hepatocellular carcinoma (HCC). Here, we observed upregulation of Sox9 in human HCC tissues compared with the non-tumorous liver counterparts (p < 0.001). Upregulation of Sox9 transcript level was associated with poorer tumor cell differentiation (p = 0.003), venous invasion (p = 0.026), advanced tumor stage (p = 0.044) and shorter overall survival (p = 0.042). Transcript levels of Sox9 and CD24 were positively correlated. Silencing of Sox9 in HCC cells inhibited in vitro cell proliferation and tumorsphere formation, sensitized HCC cells to chemotherapeutic agents, and suppressed in vivo tumorigenicity. In addition, knockdown of Sox9 suppressed HCC cell migration, invasion, and in vivo lung metastasis. Further studies showed that Sox9 endowed stemness features through activation of Wnt/β-catenin signaling, which was confirmed by the partial rescue effect on tumorigenicity and self-renewal upon transfection of active β-catenin in Sox9 knockdown cells. By ChIP and luciferase promoter assays, Frizzled-7 was identified to be the direct transcriptional target of Sox9. In conclusion, Sox9 confers stemness properties of HCC through Frizzled-7 mediated Wnt/β-catenin pathway.

SOX9 is a proliferation and stem cell factor in hepatocellular carcinoma and possess widespread prognostic significance in different cancer types

SOX9 has been previously shown to be involved in hepatocellular carcinoma (HCC) and other types of cancer. However, prognostic studies so far involved rather small cohorts or lack external validation and experimental data. In this study, we firstly determined the histological expression pattern of SOX9 in human HCC by immunohistochemistry (n = 84) and evaluated its prognostic value. External cohorts of publicly available datasets were used to validate its prognostic relevance in HCC (n = 359) and other types of cancer including breast (n = 3951), ovarian (n = 1306), lung (n = 1926) and gastric cancer (n = 876). Functional SOX9 knock-down studies using siRNA and cancer stem cell models were generated in a panel of liver and breast cancer cell lines. High level of SOX9 was associated with poor survival even after adjustment for other prognostic factors in multivariate analysis (HR = 2.103, 95%CI = 1.064 to 4.156, p = 0.021). SOX9 prevailed a poor prognostic factor in all cancer validation cohorts (p<0.05). Reduced SOX9 expression by siRNA decreased the growth of liver cancer cells (p<0.05). SOX9 expression was associated with stem cell features in all tested cell lines (p<0.05). In conclusion, this study demonstrated in a large number of patients from multiple cohorts that high levels of SOX9 are a consistent negative prognostic factor.

Repigmentation of Human Vitiligo Skin by NBUVB Is Controlled by Transcription of GLI1 and Activation of the β-Catenin Pathway in the Hair Follicle Bulge Stem Cells

Vitiligo repigmentation is a complex process in which the melanocyte-depleted interfollicular epidermis is repopulated by melanocyte precursors from hair follicle bulge that proliferate, migrate, and differentiate into mature melanocytes on their way to the epidermis. The strongest stimulus for vitiligo repigmentation is narrow-band UVB (NBUVB), but how the hair follicle melanocyte precursors are activated by UV light has not been extensively studied. To better understand this process, we developed an application that combined laser capture microdissection and subsequent whole transcriptome RNA sequencing of hair follicle bulge melanocyte precursors and compared their gene signatures to that of regenerated mature epidermal melanocytes from NBUVB-treated vitiligo skin. Using this strategy, we found up-regulation of TNC, GJB6, and THBS1 in the hair follicle bulge melanocytes and of TYR in the epidermal melanocytes of the NBUVB-treated vitiligo skin. We validated these results by quantitative real-time-PCR using NBUVB-treated vitiligo skin and untreated normal skin. We also identified that GLI1, a candidate stem cell-associated gene, is significantly up-regulated in the melanocytes captured from NBUVB-treated vitiligo bulge compared with untreated vitiligo bulge. These signals are potential key players in the activation of bulge melanocyte precursors during vitiligo repigmentation.

Discovery of novel frizzled-7 inhibitors by targeting the receptor's transmembrane domain

Frizzled (Fzd) proteins are seven transmembrane receptors that belong to a novel and separated family of G-protein-coupled receptors (GPCRs). The Fzd receptors can respond to Wnt proteins to activate the canonical β-catenin pathway which is important for both initiation and progression of cancers. Disruption of the Wnt/β-catenin signal thus represents an opportunity for rational cancer prevention and therapy. Of the 10 members of the Fzd family, Fzd7 is the most important member involved in cancer development and progression. In the present studies, we applied structure-based virtual screening targeting the transmembrane domain (TMD) of Fzd7 to select compounds that could potentially bind to the Fzd7-TMD and block the Wnt/Fzd7 signaling and further evaluated them in biological assays. Six small molecule compounds were confirmed as Fzd7 inhibitors. The best hit, SRI37892, significantly blocked the Wnt/Fzd7 signaling with IC₅₀ values in the sub-micromolar range and inhibited cancer cell proliferation with IC₅₀ values around 2 μM. Our results provide the first proof of concept of targeting Fzd-TMD for the development of Wnt/Fzd modulators. The identified small molecular Fzd7 inhibitors can serve as a useful tool for studying the regulation mechanism(s) of Wnt/Fzd7 signaling as well as a starting point for the development of cancer therapeutic agents.

FZD7 is a novel prognostic marker and promotes tumor metastasis via WNT and EMT signaling pathways in esophageal squamous cell carcinoma

Frizzled (FZD) proteins are receptors for secreted WNT proteins and play a critical role in the malignant progression of various cancers. However, the role of human FZD family members in esophageal squamous cell carcinoma (ESCC) was rarely investigated. In this study, we found that the FZD7 gene was the most commonly up-regulated FZD member in ESCC cell lines compared with other FZDs. TMA studies further validated that FZD7 protein was up-regulated in 165 of 252 (65.5%) informative ESCC patients and significantly correlated with poor overall survival (P=0.001). Additionally, multivariate Cox regression analysis showed that FZD7 overexpression was an independent prognostic factor for ESCC patients. Ectopic expression of FZD7 could promote ESCC cell metastasis both in vitro and in vivo. Under WNT3A stimulation, FZD7 was able to induce the nuclear translocation of β-catenin and activate the downstream targets of WNT/β-catenin signaling, as well as promote epithelial-mesenchymal transition (EMT) potential in ESCC cells. Our study demonstrated for the first time that FZD7 contributes to the malignant progression of ESCC and represents a novel prognostic marker and a potential therapeutic target for ESCC patients.

MicroRNA-542-3p inhibits the growth of hepatocellular carcinoma cells by targeting FZD7/Wnt signaling pathway

MicroRNAs (miRNA) are relevant regulators of the tumorigenesis of various cancers, such as hepatocellular carcinoma (HCC). Recent studies have suggested that miR-542-3p is a tumor suppressor gene in numerous cancers. However, the role of miR-542-3p in HCC remains unclear. This study showed that miR-542-3p was downregulated in HCC tissues and cell lines. MTT, colony formation, and cell cycle assays revealed that miR-542-3p overexpression inhibited HCC cell growth, whereas miR-542-3p suppression promoted cell growth. Frizzled7 (FZD7), the most important Wnt receptor involved in cancer development and progression, was identified as a functional target of miR-542-3p through dual-luciferase reporter assay, RT-qPCR, and Western blot. The mRNA expression of FZD7 was inversely correlated with miR-542-3p expression in HCC tissues. miR-542-3p overexpression could significantly decrease the activation of Wnt signaling pathway in HCC cells. FZD7 overexpression could significantly reverse the inhibitory effect of miR-542-3p on HCC cell growth and Wnt signaling pathway. Taken together, our study suggests that miR-542-3p inhibits HCC cell growth by targeting FZD7 and inhibiting Wnt signaling pathway. The decreased miR-542-3p expression may also contribute to the progression of HCC and may represent a novel molecular therapeutic target for HCC.

Biliary Phospholipids Sustain Enterocyte Proliferation and Intestinal Tumor Progression via Nuclear Receptor Lrh1 in mice

The proliferative-crypt compartment of the intestinal epithelium is enriched in phospholipids and accumulation of phospholipids has been described in colorectal tumors. Here we hypothesize that biliary phospholipid flow could directly contribute to the proliferative power of normal and dysplastic enterocytes. We used Abcb4-/- mice which lack biliary phospholipid secretion. We first show that Abcb4-/- mice are protected against intestinal tumorigenesis. At the molecular level, the transcriptional activity of the nuclear receptor Liver Receptor Homolog-1 (Lrh1) is reduced in Abcb4-/- mice and its re-activation re-establishes a tumor burden comparable to control mice. Feeding Abcb4-/- mice a diet supplemented with phospholipids completely overcomes the intestinal tumor protective phenotype, thus corroborating the hypothesis that the absence of biliary phospholipids and not lack of Abcb4 gene per se is responsible for the protection. In turn, phospholipids cannot re-establish intestinal tumorigenesis in Abcb4-/- mice crossed with mice with intestinal specific ablation of Lrh1, a nuclear hormone receptor that is activates by phospholipids. Our data identify the key role of biliary phospholipids in sustaining intestinal mucosa proliferation and tumor progression through the activation of nuclear receptor Lrh1.

Developing and characterization of single chain variable fragment (scFv) antibody against frizzled 7 (Fzd7) receptor

ABSTACT Wnt/β-catenin signaling pathway through Frizzled receptors has been shown to play a key role in both normal development and tumorigenesis. Overexpression of Wnt pathway genes, such as Fzd7 in several malignancies is well-documented. Therefore, targeting of Fzd7 and its ligand inhibits cancer cells proliferation metastasis. In the present study we isolated single chain variable fragments (scFvs) against Fzd7 receptor using phage display method. Semi-synthetic human naive antibody libraries (Tomlinson I + J) was employed in panning procedure to isolate specific scFv against specific peptide from extracellular domain of Fzd7 receptor. The reactivity and growth inhibition effects of the selected antibodies was evaluated using enzyme-linked immunosorbent assay (ELISA), MTT and annexin V assays, respectively. Seven scFvs reactive to Fzd7 were selected following 4 rounds of panning. The results showed that the selected scFvs inhibits cell growth through apoptosis cell death in a triple negative breast cancer cells, MDA-MB-231. Given that Fzd7 and Wnt pathway plays a critical role in tumor progression, selected blocking scFvs represent significant potential for immunotherapy of breast cancer cells.

MicroRNA-27b suppresses Helicobacter pylori-induced gastric tumorigenesis through negatively regulating Frizzled7

MicroRNAs (miRNAs) are novel tools for cancer therapy. Frizzled7 (FZD7) is an important co-receptor in the WNT signaling pathway. The WNT signaling pathway is aberrantly activated in Helicobacter pylori (H. pylori)‑infected gastric cancer cells. However, the role of FZD7 in H. pylori‑induced gastric tumorigenesis remains unknown. In this study, we investigated the potential role of FZD7 in H. pylori-induced gastric tumorigenesis and validated the possibility that targeting of FZD7 by specific miRNA inhibits H. pylori-induced gastric tumorigenesis. First, we found that FZD7 was significantly induced by H. pylori infection in a dose- and time-dependent manner. Knockdown of FZD7 by FZD7 small interfering RNA effectively inhibited H. pylori infection-induced cell proliferation of gastric cancer cells. We found that microRNA-27b (miR-27b) was the predicted miRNA for FZD7 and that miR-27b negatively regulated FZD7 expression by targeting the 3'-untranslated region of FZD7. Furthermore, miR-27b overexpression significantly inhibited H. pylori infection-induced cell proliferation and WNT signaling pathway activation in gastric cancer cells. Restoration of FZD7 expression significantly attenuated the inhibitory effect of miR-27b overexpression on cell proliferation and WNT signaling pathway activation. Collectively, our study suggests that FZD7 triggered by H. pylori infection contributes to the H. pylori infection-induced cell proliferation that links the WNT. Thus, miR-27b may be a promising molecular target for the treatment of the disease.

MicroRNA-613 represses prostate cancer cell proliferation and invasion through targeting Frizzled7

A growing number of studies have indicated that microRNAs (miRNAs) are critical regulators of carcinogenesis and cancer progression and may serve as potential therapeutic tools for cancer therapy. Frizzled7 (Fzd7), the most important receptor of the Wnt signaling pathway, is extensively involved in cancer development and progression. However, the role of Fzd7 in prostate cancer remains unclear. In this study, we aimed to explore the expression of Fzd7 in prostate cancer and test whether modulating Fzd7 expression by miR-613 would have an impact on prostate cancer cell proliferation and invasion. We found that Fzd7 was highly expressed in prostate cancer cell lines. Through bioinformatics analysis, Fzd7 was predicted as a target gene of miR-613, which was validated by dual-luciferase reporter assays, real-time quantitative polymerase chain reaction and Western blot analysis. By gain of function experiments, we showed that overexpression of miR-613 significantly suppressed prostate cancer cell proliferation and invasion. Furthermore, miR-613 overexpression markedly downregulated the Wnt signaling pathway. Through a rescue experiment, we showed that overexpression of Fzd7 could abrogate the inhibitory effect of miR-613 on cell proliferation and invasion as well as Wnt signaling. Additionally, these results were further strengthened by data showing that miR-613 was significantly downregulated in prostate cancer tissues, exhibiting an inverse correlation with Fzd7 expression. In conclusion, our study suggests that miR-613 functions as a tumor suppressor, partially through targeting Fzd7, and is a potential therapeutic target for prostate cancer.

Frizzled-7 promoter is highly active in tumors and promoter-driven Shiga-like toxin I inhibits hepatocellular carcinoma growth

Frizzled-7 protein plays a significant role in the formation of several malignant tumors. Up regulation of the Frizzled-7 in cancer cell lines is associated with nuclear accumulation of wild-type β-catenin from the Wnt/β-catenin pathway which is frequently activated in tumors. To analyze activity of the Frizzled-7 promoter in tumor cells, we constructed two recombinant plasmid vectors in which the Frizzled-7 promoter was used to drive the expression of green fluorescent protein (GFP) and Shiga-like toxin I (Stx1) (pFZD7-GFP/Stx1) genes. The Frizzled-7 protein was found to be expressed in the cancer cell lines but not in the normal cell lines. The GFP expression was restricted to the cancer cell lines and xenografts in the BALB/C mice but not to normal cell lines. Moreover, cell proliferation and tumor growth decreased significantly after transfection with the pFZD7-Stx1. Results from this study will help determine a highly effective strategy for gene therapy of tumors.

Structure-based Discovery of Novel Small Molecule Wnt Signaling Inhibitors by Targeting the Cysteine-rich Domain of Frizzled

Frizzled is the earliest discovered glycosylated Wnt protein receptor and is critical for the initiation of Wnt signaling. Antagonizing Frizzled is effective in inhibiting the growth of multiple tumor types. The extracellular N terminus of Frizzled contains a conserved cysteine-rich domain that directly interacts with Wnt ligands. Structure-based virtual screening and cell-based assays were used to identify five small molecules that can inhibit canonical Wnt signaling and have low IC₅₀ values in the micromolar range. NMR experiments confirmed that these compounds specifically bind to the Wnt binding site on the Frizzled8 cysteine-rich domain with submicromolar dissociation constants. Our study confirms the feasibility of targeting the Frizzled cysteine-rich domain as an effective way of regulating canonical Wnt signaling. These small molecules can be further optimized into more potent therapeutic agents for regulating abnormal Wnt signaling by targeting Frizzled.

Activation of signal transduction pathways during hepatic oncogenesis

BACKGROUND AND AIMS

Understanding the molecular pathogenesis of hepatocellular carcinoma (HCC) is essential to identify therapeutic targets. A hepatitis B virus (HBV) related double transgenic murine model was developed.

METHODS

Liver specific expression of HBV X protein (HBx) and insulin receptor substrate 1 (IRS1) was achieved and transgenic mice were followed from birth to age 21 months. Liver and tumor tissue were assessed for histologic changes as well as activation of signal transduction pathways by qRT-PCR and multiplex ELISA protein assays.

RESULTS

Overexpression of HBx and IRS1 stimulates liver cell proliferation in the double transgenic mice. Only the male mice developed HCC starting at age 15-18 months. The IN/IGF1/IRS1/MAPK/ERK and IN/IGF1/IRS1/PI3K/AKT/GSK3β cascades were activated early (6-9 months) in the liver followed by WNT/β-catenin and Notch signaling. Aspartate β-hydroxylase (ASPH) was found to link these upstream growth factor signaling pathways to downstream Notch activation in tumor tissues.

CONCLUSIONS

Sustained overexpression of HBx and IRS1 led to constitutive activation of a tripartite growth factor signal transduction cascade in the liver and was necessary and sufficient to promote HCC development and progression.